‘Unto dust shalt thou return’ - Hayabusa2´s discovery of asteroid regolith properties

The surfaces of small asteroids recently sampled by the Hayabusa2 and OSIRIS-REx missions are largely covered by a regolith of decimetre-sized or smaller particles. In the past, the origin of this regolith had been attributed to impact-related processes alone.

These days however, thermal fatigue is being touted as a relevant, possibly the dominant, process for the production of regolith on airless bodies.

Many unanswered questions remain regarding the effectiveness of thermal fatigue vis-à-vis impacts because the principal parameters controlling the breakup mechanism are largely unknown.

With Hayabusa2 and OSIRIS-REx samples soon to undergo analysis on Earth, we need to understand the processes that created the regolith particles which will be analysed.

This project, enabled by the lead applicant’s role on JAXA’s Hayabusa2 mission, will determine if, and under which circumstances, thermal fatigue can really be a dominant process in the production of regolith on solar system bodies, and whether its signatures can be identified in the asteroid samples returned to Earth.